Re-configuration in a digital network

ABSTRACT

A method for executing a re-configuration in a self-configuring digital network after occurrence of a reconfiguration trigger, through upon detecting such trigger, communicating between various physical nodes their respective logical node identifiers and furthermore functionality informations regarding the respective node stations,  
     said method being characterized by, associated to such detecting, recognizing in a particular node such other nodes that are conducting a communication relation with said particular node, marking all logical node mappings on the various physical nodes as invalid, through said communicating of logical node identifiers establishing said reconfiguration, whilst executing communicating said functionality informations on a basis of necessity.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method for executing are-configuration in a self-configuring digital network after occurrenceof a re-configuration trigger. A non-limiting example of such network isthe Serial Bus Network IEEE 1394-1995 as discussed in International PCTPatent Application WO 00/23869. This standard allows a plug-and-playfeature, and although originally intended for computer-basedapplications, has been introduced also into in-home consumer-electronicnetworks. Its prime definition level is the physical level. Variousmodifications and extensions to the standard have been implemented inStandards 1394A2000 and P1394.1. Still another feasible embodiment forthe present invention is the USB bus standard.

[0002] The above standards have been combined with the HAVI or HomeAudio/Video Interoperability principles that operate on a conceptuallevel. This allows to combine of controller devices or nodes withcontrolled devices or nodes. In such combination, the user-level audioand/or video data will travel as isochronous streams, whereas controlsignals will travel in an asynchronous manner.

[0003] Now, in such network, various incidents may cause suchreconfiguration trigger signal, such as the adding or removing of aparticular station, or a change of status in a particular station.However, other causes may also generate such trigger signal. The vehicleof the trigger signal may be a bus reset. In principle, all kinds ofchange may have occurred after such bus reset. The inventor hasrecognized that in general however, no change will have occurred at all.Such would then allow for executing a much simplified procedure. More inparticular, the invention relates to a method as recited in the preambleof independent claim 1 hereinafter.

[0004] In this respect, the abstract of the above PCT reference recitesthat the controlling application utilizes so-called handle objects toreconfigure objects to dynamically enumerate and represent devices thatare coupled to a serial bus network after a bus reset event. During aself-identifying process, following the bus reset, information about thecharacteristics of the devices within the network will be received. Fromthe self-identifying information, objects are generated that representthe various devices. Existing handle objects from a previous busconfiguration are then compared to these newer objects. If a handleobject would match such newer object, then a pointer value within thehandle object will be changed to point to an address of the newerobject. For devices that have been removed from the network, the handleobject will preferably never be discarded, but is rather made invalid.

[0005] Now, according to the present invention, upon occurrence of suchre-configuration trigger, the logical configuration of the network mustbe established again. In certain circumstances, this may require aninappropriately long time, inter alia, because certain stations may needto exchange a large amount of information with one or more otherstations, and/or certain stations may feature a large inherent delaybefore they will be fully operational again. The inventor has recognizedhowever, that one or more parts of the network could take up theirrespective operations again, even if certain other stations outside thepart or parts in question were still busy with recuperating. In thisrespect, the P1394.1 standard would even allow the forming of in-networkclusters of nodes.

SUMMARY TO THE INVENTION

[0006] In consequence, amongst other things, it is an object of thepresent invention to let those ones among the stations that lie in suchpart as recited resume their particular operations, if no obstaclesagainst such operations would anymore exist, even if certain otherstations outside the above part or parts in question were still busywith recuperating. Such inter alia would render the operation of thenetwork much more stable, in that generally, pre-existing operationalrelationships between the nodes would be taken up again more or lessimmediately.

[0007] Now therefore, according to one of its aspects the method of thepresent invention is characterized according to the characterizing partof claim 1. Herein, the necessity implies all that is necessary forproceeding with the ongoing operations of the network, including ofcoping with possible contingencies. In this respect, the reference hasindeed the transmitting of the device characteristics even to physicaldevices with which the transmitter station had not been cooperating.Waiting until completion thereof would clearly take an inappropriatelylong time.

[0008] The invention also relates to a system arranged for implementinga method according to the present invention as claimed in claim 6, andto an apparatus being arranged to operate as a node station in suchsystem and as claimed in claim 7. Further advantageous aspects of theinvention are recited in dependent Claims.

BRIEF DESCRIPTION OF THE DRAWING

[0009] These and further aspects and advantages of the invention will bediscussed more in detail hereinafter with reference to the disclosure ofpreferred embodiments, and in particular with reference to the appendedFigures that show:

[0010]FIG. 1, a logical node mapping of a network before an initialevent;

[0011]FIG. 2, a first logical node mapping of a network after an initialevent;

[0012]FIG. 3, a second logical node mapping of a network after aninitial event;

[0013]FIG. 4, a general binary tree network for use with the invention;

[0014]FIG. 5, a flow chart of the operations executed according to apreferred embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0015] A digital network such as, but not being limited to, a homenetwork, will generally consist of a set of nodes interconnected bypoint-to-point physical links. The nodes may represent various userfunctionality devices, such as audio and/or video components, securitycameras, household appliances, antenna disk or other external linkstations, and also system-level devices, such as subaltern networks. Inresponse to an initial event such as a bus reset, the network will bereconfigured and a new logical view of the overall status of the networkmust be created. For each respective node, this logical view or topologymap will comprise the relevant node itself, its interconnections, andsuch additional functional or other information of the relevant nodes aswould be appropriate. Other nodes will collect this additionalinformation for each particular logic node as being based on theidentifier of that particular node. After the reconfiguration, next tothe local view, one or more of the nodes will store an overall logicalview of the network. This overall view may be interrogated by othernodes according to need, until a next reconfiguration will occur. Thisnew reconfiguration will then again cause the setting up of a new oramended overall logical view, which may then even be stored on adifferent node from before.

[0016] The above initial event will cause an unstable situation in thenetwork. Such unstable situation may be aggravated because various nodeswill need respective different amounts of time to recover from theunstable situation, included therein a time period that is necessary forthe generating or receiving of the additional information, such asfunctional information, on a per node basis. This functional informationmay by way of example include various operational parameters orinterface definitions. The heavy bus traffic necessary for effectingthis communication may contribute to the system instability, because inprinciple, each node would need to have its own, possibly partialknowledge of the logical view of the overall network. Such acquiring ofthe overall view may in fact be executed in that a node wouldinterrogate the node that stores the topology map. Another feasiblestratagem were that each node would itself compose such logical mapview. The latter procedure may result in unnecessary waste of bandwidthdue to failed transactions requests to a node that is not yet ready forcommunicating, or in incomplete and/or inconsistent logical views atseveral nodes. There will in fact be no guarantee that all preliminarylogical views will be identical.

[0017] The present invention applies selective topology, which allowsthe network to stabilize in a felicitous manner. Immediately after theevent leading to the bus reset or trigger signal, the present inventionwill minimize the amount of communication. In fact, the inventor hasrecognized that it is generally not necessary to update allfunctionality information. The additional or functional information thatuniquely identifies the physical node and its appropriate propertieswill always remain unchanged as long as the associated device remains inplace, although its mapping on the logical identifier may be changed. Itis thus proposed to only update the required information of thecommunicating nodes. Each node only has to store the additionalinformation of the node or nodes it has a communcation relation with.After the initial event, the inventive idea is to take no actions on thenetwork, but to only mark all available mappings as invalid. Thismarking will indicate that the stored information could still beup-to-date indeed, and that it might be re-used in the future. If thenode in question has to communicate with another node marked invalid,for the first time after the initial event, the former will checkwhether the original mapping of the node on a particular device is stillvalid, through an information query to the corresponding node, and itwill only selectively update the mapping according to necessity. If themapping is invalid however, such as through removing or replacing of anapparatus, a network-wide query will be issued instead to update themapping. The Selective Topology Mapping according to the presentinvention will allow the network to stabilize (it will delay the firstnetwork access), reduce the number of network accesses (use lessbandwidth), and generally, increase overall efficiency.

[0018]FIG. 1 illustrates a logical node mapping of a network before aninitial event. For demonstration purposes, only a small-size network hasbeen shown, but all aspects thereof would upscale immediately to alarger network. In the embodiment, device A is a video storageapparatus, device B a disc antenna station, device C a television set,and device D a camera. Many other categories of devices would befeasible, as discussed earlier. The logical node identifiers have beenindicated for each device or physical node. Device A, with nodeidentifier #1 stores the overall logical view of the network. By way ofexample, Devices A and C are maintaining a video stream, for example,while running and displaying a video title. Accessing in the network isalways based on the logical node identifier.

[0019] Furthermore, the arrangement embodiment carries the assumptionthat device D will need relatively much time for recovering from theinitial event, and in such interval would not be available to supplyinformation to any of the other devices. This means that with respect tothis device D, the overall network topology will not be complete beforethe termination of the above recovery time. However, as far as onlyconsidering the maintaining of the above video stream, the overallnetwork could become operational much faster, i.e., as soon as devices Aand C will have checked that their respective mappings have beenunchanged, or rather, found out enough details on their respectivewhereabouts and functionality. The same would apply to the replacing ofone of the two devices, as far as this replacing would not influence themode of operation. For example, another video storage apparatus wouldneed the same cassette and would have to be controlled in the samemanner as its predecessor.

[0020]FIG. 2 illustrates a first logical node mapping of a network asamended after an initial event that were to generate the describedtrigger signal, but with the devices located as in FIG. 1. As shown,device A has maintained its logical identifier, whereas all otherdevices or nodes have gotten different logical identifiers from thesituation in FIG. 1.

[0021]FIG. 3 illustrates a second logical node mapping of a networkafter a similar initial event as in FIG. 2, but for the remainder,unchanged. Again, various devices have gotten different identifiers.

[0022]FIG. 4 illustrates a general binary tree network for use with theinvention; no configuration with loops will be considered. In theembodiment, root node 120 has a map of the logical network. As shown,other nodes 122 through 140 are interconnected in such manner that eachnode has zero, one or two connected nodes in a next higher networklayer. Nodes 124, 126, 134, 136 and 140 are leaf nodes in that theyconnect no node at a higher layer level. In principle, higher numbersfor the interconnection multiplicity are feasible. In practice, anynetwork size could do. The same network may also be represented byrearranging the nodes into a different configuration, leaving thevarious connections unchanged.

[0023]FIG. 5 illustrates a flow chart of the operations executedaccording to an exemplary embodiment of the present invention. In block20, the operation starts, and all necessary hardware and softwarefacilities are assigned. In block 22, a Bus Reset signal is detected. Ofcourse, such detecting may be effected through circling in a waitingloop, and this detecting would then represent a “detect-YES” exit of theloop. Now, in block 24, all ongoing communication operations areinterrupted. In block 26, the pre-existing communication pattern isrecognized by the node in question and saved in a local storagefacility. This will include all ongoing communications as well ascommunication relations that for the moment had been inactive, but couldbecome active if required. Next, in block 28 all mappings of the logicalnodes on the physical nodes are made invalid. In block 30, the variousnodes will start undertaking to effect a new mapping pattern that wouldbe appropriate for the overall configuration. Such undertaking may bebased on the node's self-identifier assigned under the 1394 standard,and be executed first on the tree level of node itself. A particulardevice would first try to monopolize the associated tree level throughusing a timer functionality and its self-identifier, and tentativelyassign to itself a logical mapping number. This number will then bebroadcast on that tree level, for consent by the other connected nodesor otherwise. In block 32, this consent (Y), or dissent (N) is detected.Next, in block 34, the mapping is stored. To this effect, the HAVIorganization must find out all changes that have been effected andretrieve the associated information, by putting the appropriatequestions to all devices concerned. This operation then proceeds for theother nodes on the tree level in question, which has not been explicitlyshown, and also on the other tree levels. If the mapping isunrestorable, a network-wide query is undertaken for a replacementtarget node for such mapping.

[0024] In block 36, the device in question will detect wether allmappings for letting the device in question resume its communicationpattern have succeeded. If not yet (N), the device reverts to block 32to find such other mapping. For reference, in the mapping patterns ofFIGS. 1-3, after a bus reset, two stations donot have to find anyoutside mapping at all, whereas the other two stations should each findonly one external mapping before being able to resume operations. Aftercompletion of the local mapping (block 36 YES), the devices willtransfer their functionality information to those other stations thatneed to know but have not yet gotten the information in question. Inblock 40, a READY? detection is executed. If not, the system reverts toblock 32. Such case may for example be caused in that a subalternmapping is still necessary. If ready, the operation of the network partis resumed. The formation of a global mapping pattern in one or moreparticular devices has not been illustrated in this Figure. Such storingmay be undertaken in a root node that is specifically adapted, such asin FIGS. 1-3. Storing in more than one node could be useful as well.Note that other various devices may already have reached the end of thisflow chart, whereas other devices could still be lingering in blocks 32or 38.

1. A method for executing a re-configuration in a self-configuringdigital network after occurrence of a reconfiguration trigger, throughupon detecting such trigger, communicating between various physicalnodes their respective logical node identifiers and furthermorecommunicating functionality informations regarding the respective nodestations, said method being characterized by, associated to suchdetecting, recognizing in a particular node such other nodes that beforesuch trigger had been conducting a communication relation with saidparticular node, marking all logical node mappings on the variousphysical nodes as invalid, through said communicating of logical nodeidentifiers establishing said reconfiguration, whilst executing thecommunicating of said functionality informations on a basis ofnecessity.
 2. A method as claimed in claim 1, wherein suchreconfiguration undertakes to re-establish an existing mapping patternof logical identifiers from a hitherto communication-related sub-setsamong said nodes, whilst seeking replacement of interruptedcommunication-relations on a basis of necessity.
 3. A method as claimedin claim 1, wherein upon detection of an unvalid and unrestorablemapping, a network-wide query is undertaken for a replacement targetnode for effecting such mapping.
 4. A method as claimed in claim 1,whilst in association with said reconfiguration storing an overallnetwork topology in a subset made up of one or more physical nodes ofthe network.
 5. A method as claimed in claim 1, wherein said network isbased on IEEE 1394 or USB.
 6. A system being arranged for implementing amethod as claimed in claim 1, and having reconfiguring means forexecuting a re-configuration in a self-configuring digital network afteroccurrence of a reconfiguration trigger, comprising detection means fordetecting such trigger, communicating means for thereupon communicatingbetween various physical nodes their respective logical node identifiersand furthermore communicating functionality informations regarding therespective node stations, said system having recognizing means for,associated to such detecting, recognizing in a particular node suchother nodes that before such trigger had been conducting a communicationrelation with said particular node, marking means for marking alllogical node mappings on the various physical nodes as invalid, and saidcommunicating means being operative for through said communicating oflogical node identifiers establishing said reconfiguration, whilstexecuting the communicating of said functionality informations on abasis of necessity.
 7. An apparatus being arranged for operating as anode station in a system as claimed in claim 6.